Hydraulic tappet



March 13, 1956 o. H. BANKER 2,737,934

HYDRAULIC TAPPET Filed Jan. 15, 1955 IN VEN TOR.

United States Patent() "cc HYDRAULIC TAPPET Oscar H. Banker, Evanston, 11]., assignor to New Products Corporation, Chicago, Ill., a corporation of Delaware Application January 13, 1953, Serial No. 330,973

9 Claims. (Cl. 12390) This invention relates to improved hydraulic tappets for the transmission, of force between an actuating member, such as a rotary cam, and an engine valve of the poppet type, being more particularly concerned with the provision of a tappet which is self-compensating under anyand all conditions. This is a continuation in part of my copending application, Serial No. 744,975, filed April 30, 1947, now abandoned.

It is a general object of the invention to provide a tappet of the foregoing description, primarily intended for'use as a replacement installation but also well adapted for use as original equipment, which embodies provisions for preventing entrainment of air in the operating liquid thereof, while securing optimum timing of the opening and closing of an engine intake or exhaust valve.

A further and more specific object is to provide a hydraulic tappet adapted to maintain constant contact with a. valve or like member controlled or actuated thereby, which tappet, in one form chosen for illustration, has provision to automatically compensate for variations in the size of said member by afiording a phase-in its cycle of operation during which the tappet isineifective to actuate or shift the member.

A general object is to provide different embodiments of improved hydraulic tappet, preferably though not necessarily an entirely self-contained one, which are characterized in common by provisions to prevent the entrapment of air in a compression chamber portion of the tappet by affording separate but communicating primary and secondary liquid reservoir compartments within the tappet, which compartments insure that liquid drawn into said compression chamber in the operation of the tappet is absolutely free ofentrained air.

More specifically, it. is an object to provide an improved, self-contained, divided reservoir type of hydraulic tappet; as described in the preceding paragraph, which in one embodiment is. characterized by a plunger past which leak-by-liquid from a compressionchamber on'one side of: the plunger is returned directly to a lower, primary cavity ofthe divided reservoir; and which in another embodiment features a plunger past which leak-by liquid from the compression chamber is returned to an upper, secondary cavity of the divided reservoir.

Theforegoing. statements are indicative in a general way of, the nature of: the invention, but other and'more specific objects will be apparent to those skilled in the art upon a full understanding. of the construction and operation of the device.

Two embodiments of the invention are presented herein for purpose of exemplification, but it will be appreciated that the invention may be incorporated in other modified forms coming equally within the scope of the appended claims.

In the drawings:

Fig. 1 is a view invertical section through the axis of one form of tappet in accordance with the invention,

having features insuring against the entry of entrained. air.- in'thecompression chamber of thetappet during 2,737,934 Patented Mar. 13, 1956 operation, and also having provisions to effect a delayed action valve lifting stroke;

Fig. 2 is a view in transverse section similar to Fig. 1, showing a further modification of the divided reservoir feature of the tappetof Fig. 1; and

Fig. 3 is a top plan'view of the tappet of Fig. 2.

In the form of the invention illustrated in Fig. 1, the reference numeral 10 designates an external, elongated; hollow cylindrical tappet body which is reciprocably actuated by' a conventional cam C. A two-part hydraulic plunger 11 is'disposed in the body 10 for axial movement relative thereto, this plunger comprising an upper, hollow cylindrical'plunger member 12 and a lower hollow cylindrical piston member 13 on which the member 12 rides. The member 12 is provided at its lower end with a hollow, inverted and axially apertured, thimble-like insert 14, which is sleeved into the lower end of plunger member 12 and brazed thereto at 15 to constitute in elfect a chambered unitary plunger structure. Insert 14 carries an external peripheral groove 16 in which the synthetic rubber sealing ring 17 is disposed forliquid-tight sealing engagement with the internal surface of body 10. An absolute liquid seal is produced at this point.

The insert 14 affords a primary liquid chamber 18 in the plunger member, which communicates through the small central insert aperture 19 with the larger secondary reservoir20 in the interior of said hollow plunger member 12 immediately above insert 14. The upper end of plunger member 12 is shaped to provide an anvil 21 which maintains continuous contact with the valve stem S or corresponding member. A split expanding ring 22 which is received in an internal groove at the upper end of tappet b0dy'10 servesas a stop coacting with an annular shoulder 23'on the plunger 12 to restrain upward movement of the latter when the tappet is in free, uncompressed condition.

As stated above, the plunger member 12 rides on the piston member 13, which latter is spring urged upwardly by a coil'spring 24 in the tappet body to maintain contact ofthe plunger and body with the valve stem and tappet respectively. Said coil spring rests at its lower end on the bottom of the compression chamber 25 in the body and -at its upper end it abuts and holds in place the apertured ball check cage or cup 26, the rim of which in turn bears against an internal annular flange or shoulder of the hollow piston member 13.

A feature of the embodiment shown in Fig. 1 is that the time required for-the ball check 28 to rise from the lower passage-exposing position thereof in Fig. l to its upper, passage-sealing position i. e., against an annular tapered sealing surface29 adjoining a central bore 27 of piston member 13, is accurately correlated withand preferably equated to the duration of the initial, partial rotation of cam C, in which opening of the valve is not intended to take place This phase corresponds to the phase of inoperation afiorded by the intentional clearance between valve and tappet provided for in an original mechanical tappet installation.

Piston member 13 has a relatively close tolerance fit= in the, interior of bodyv member 10, however, in the event, of elongation of the valve stem S in operation, a controlled, slow escape of liquid may take place between said piston memberand body to compensate this elongation and equalize the pressure in chamber 25.

The tappet of Fig. l contemplates the existence of'a space 30 above the level of liquid in the hollow plunger 13thereof, serving as an air or expansion chamber. Considerable difficulty has been experienced in previous hy draulictappets due to the tendency of air becoming entrained and emulsified in the compression liquid and being rendering the tappet unreliable in operation. The structure illustrated in Fig. 1 provides a secondary reservoir chamber 29 in which air may be present with the pressure liquid, together with a primary reservoir chamber 18 communicated with said secondary chamber only by a small connecting hole for the express purpose of eliminating the condition referred to. 1 have found that even though considerable disturbance or turbulence may exist in said secondary chamber 20 during fast reciprocating movement of the tappet, accompanied by mixing of air with the liquid, the condition is confined to the secondary chamber. The liquid in primary chamber 18 remains in purely liquid, uncontaminated condition and relatively quiescent. As the piston member 13 shifts relative to body 19, to displace liquid from chamber 25 on one stroke and draw liquid into the chamber on the opposite stroke, this liquid remains air-free due to the provision of primary chamber 18.

It is accordingly immaterial whether air at atmospheric or subatmospheric pressure, or even compressed air, exists in the secondary reservoir chamber 20 or expansion chamber 36, or whether the liquid in said secondary chamber is emulsified. The mechanically divided chamber arrangement insures that none of this air will be delivered to the compression space 25.

The divided reservoir tappet described above features a plunger unit in which pressure sealing of the compression chamber is performed by an O-ring on the unit in sealing engagement against the inner wall of the tappet body. Liquid leak-by past member returns directly to primary reservoir chamber 18. The modified and simplified embodiment illus rated in Figs. 2 and 3 of the drawings provides a self-contained tappet having a divided reservoir construction of the same general type as is illustrated in Pi". 1; however, in this form the leak-by liquid is returned to the upper or secondary chamber of the divided reservoir. An O-ring is employed to seal the tappet body at its upper end against escape of liquid to atmosphere. As in the first form, churning and aeration of liquid directly supplied to the compression chamber of the tappet, as the result of high speed tappet operation, are prevented, the fluid in the compression chamber and the primary reservoir chamber leading thereto being kept 100% liquid at all times.

Referring to Figs. 2 and 3, a hollow cylindrical body 32 slidably receives a hollow cylindrical plunger or plunger device, generally designated 33, which is essentially made up of a reservoir-defining member 3a, which is of hollow, inverted cup-like, axially apertured shape, and an upper closure and thrust transmitting member 35. This mernher is fitted in the cylindrical upper end of member 34 and is loose in the latter.

Plunger member 33 has a very close tolerance fit in the upper cylindrical portion of member 32, and an O- ring 36 is mounted in an annular peripheral groove 37 in plunger closure member 35. This is for the sole purpose of sealing tappet body 32 against the escape of liquid to the atmosphere; it will be noted that the member 35 has substantial radial clearance in the tappet body. A split snap ring coacts with member 35 to limit upward movement of plunger 33, the snap ring being received in an internal groove adjacent the upper end of tappet body 32.

An oil drainage passage 39 is drilled in plunger closure member 35 to communicate O-ring groove 3? with the hollow interior of the plunger member 34, which serves as a reservoir cavity for the plunger. Passage 39 returns lealeby or oil which works upwardly between plunger 33 and tappet body 32 to the upper part of this cavity.

The cavity is subdivided into a lower or primary reservoir 4G and an upper or secondary reservoir ll by means of a partition member or bafile 42'. Battle 42 may be in the form of a generally circular sheet metal stamping which is radially milled and bent 90 about its periphery to define circumferentially separated friction holding elements 43 disposed normal to the transverse baffie portion of member 42. Passages 4-4 of restricted size between the depending elements 43 communicate primary and secondary reservoirs 40, 4-1 with one another, the passages extending through said transverse bafiie portion at the sides thereof.

The lower extremity of plunger member 34 is extruded or otherwise formed radially inwardly in the shape of a horizontal bottom wall 45 of annular outline, which is brought downwardly at 46 in the form of a central apertured nipple. The lower internal edge 47 of nipple 46 serves as a valve seat against which a ball check 43 engages to seal off flow through the nipple on the compression stroke of the tappet. A perforated, radially flanged, thimble-shaped cage 49 holds ball check 43 adjacent valve seat 47, the thimble being sleeved upwardly over nipple 46, with its flange 50 abutting the annular lower Wall 45 of plunger member 34. A coil compression spring 51 acts between flange 5t) and the bottom of tappet body 32 to maintain the cage in proper position.

Partition member or baffle 42 alfords a two-chamber reservoir, in which aeration of liquid adjacent the one way passage at nipple 4-6, i. e. the liquid in primary reservoir 4-0, is protected against churning, frothing or aeration under rapid reciprocation of the tappet.

While the two tappet embodiments shown in Figs. 1 and 2 are self-contained ones, in that they have their own permanent charge of hydraulic fluid, it is to be understood that the principles of the invention are adaptable to an externally supplied tappet.

I claim:

1. A hydraulic tappet comprising a hollow tubular body, a plunger device shiftable axially in and relative to said body in liquid-tight sealed relation thereto, said plunger device including means defining a reservoir within the same having upper and lower liquid chambers of substantial liquid receiving capacity, said reservoir chambers having restricted but direct and open communication with one another such as to maintain said lower chamber free of air, said plunger device and body defining therebetween a compression chamber and said device having a passage communicating with said compression chamher, said passage being in direct, unrestricted communication with the entire interior of the lower reservoir chamber, and a control element positioned adjacent said passage to control flow of liquid therethrough from said lower chamber to said compression chamber.

2. A hydraulic tappet in accordance with claim 1 in which a lower portion of said plunger device adjacent said compression chamber affords a liquid leak-by path between said device and said body, and in which a portion of said plunger device above said leak-by path is provided with a resilient annular sealing member in absolute sealing engagement with said body.

3. A hydraulic tappet comprising a hollow outer body, an inner plunger mounted in said body, said plunger and body defining a compression chamber therebetween, said plunger being hollow and having means subdividing the interior thereof into upper and lower liquid receiving chambers and means communicating said chambers directly and openly but sufficiently restrictedly with one another to maintain the lower chamber free of air, said plunger having a passage communicating said lower chamber with said compression chamber, said passage having free and unrestricted communication with the entirety of said lower chamber, a control element for said passage, said plunger being provided with an annular groove adjacent the top thereof, and an annular memher in said groove engaging said body wall to prevent escape of liquid.

4. A hydraulic tappet comprising a hollow outer body, an inner plunger mounted in said body, said plunger and body defining a compression chamber therebetween, said plunger being hollow and having means subdividing the interior thereof into upper and lower liquid receiving chambers and means communicating said chambers directly and openly but sufficiently restrictedly with one another to maintain the lower chamber free of air, said plunger having a passage communicating said lower chamber with said compression chamber, said passage having free and unrestricted communication with the entirety of said lower chamber, a control element for said passage, said plunger being provided with an annular groove adjacent the top thereof, and an annular member in said groove engaging said body wall to prevent escape of liquid, there being a liquid return passage in said plunger communicating said groove with said upper chamber.

5. A hydraulic tappet comprising a hollow outer body, an inner plunger mounted in said body, said plunger and body defining a compression chamber therebetween, said plunger being hollow and having means subdividing the interior thereof into upper and lower communicating, liquid receiving chambers, comprising an axially flanged plate fixedly mounted in said interior and provided with circumferentially spaced openings at its perimeter, said openings directly and openly communicating said upper and lower chambers with one another but being sulficiently restricted in their aggregate size to maintain said lower chamber free of air, said plunger having a passage communicating said lower chamber with said compression chamber, said passage having free and unrestricted communication with the entirety of said lower chamber, a control element for said passage, said plunger being provided with an annular groove adjacent the top thereof, and an annular member in said groove engaging said body wall to prevent escape of liquid.

6. A hydraulic tappet comprising a hollow outer body, an inner plunger mounted in said body, said plunger and body defining a compression chamber therebetween, said plunger being hollow and having means subdividing the interior thereof into upper and lower, liquid receiving chambers, comprising an axially flanged plate fixedly mounted in said interior and provided with circumferentially spaced openings at its perimeter, said openings directly and openly communicating said upper and lower chambers with one another but being sufiiciently restricted in their aggregate size to maintain said lower chamber free of air, said plunger having a passage communicatingfsaid lower chamber with said compression chamber, said passage having free and unrestricted communication with the entirety of said lower chamber, a control element for said passage, said plunger being provided with an annular groove adjacent the top thereof, and an annular member in said groove engaging said body wall to prevent escape of liquid, there being a liquid return passage in said plunger communicating said groove with said upper chamber.

7. A hydraulic tappet in accordance with claim 1, in which said reservoir defining means comprises a transversely extending plate fixedly mounted within said plunger device to subdivide its interior into said chambers, said plate having axially extending openings of restricted transverse size providing for said restricted communication of said chambers.

8. A hydraulic tappet in accordance with claim 1, in which said reservoir defining means comprises a member fixedly telescoped in said plunger device to subdivide the same into said upper and lower chambers, said member being axially apertured at its center to provide said restricted communication of the chambers.

9. A hydraulic tappet in accordance with claim 8, in which said plunger device comprises a pair of separate plunger members in axial abutment with one another, said subdividing member being upwardly telescoped in the upper of said plunger members and having a downwardly opening space between the aperture therein which defines the lower liquid chamber. 3

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